I'd suspect this is because Microsoft doesn't export that information when converting to PDF.
There are scads of other converstion to PDF options, my favorite being PDFCreator. I'd advise trying a couple of different ways of creating the PDF from an MS-Word file and see if any of them result in that information being carried over.
PDFs definitely have the capability of having this sort of information embedded if memory serves, so if it's there in an original in another format and missing from a converted-to-PDF document I'd suspect the conversion process.
Brian - Windows 10 Pro, 64-Bit, Version 20H2, Build 19042
Always remember others may hate you but those who hate you don't win unless you hate them. And then you destroy yourself.
~ Richard M. Nixon